The present invention relates to a wiring structure and a resin sealing structure in a power semiconductor module, in particular, to a wiring structure and a resin sealing structure in a power semiconductor module, where high reliability and longer-life under severe use environment are required, like an IGBT (Insulated Gate Bipolar Transistor) module for automobile use typified by hybrid vehicle applications.
In a power semiconductor module such as an IGBT module for controlling an electric current of several amperes to several-hundred amperes, still more about one thousand amperes, it is general that an electrode at the surface of a power semiconductor chip, and an external circuit pattern are connected with an aluminum wire. This aluminum wire is bonded to an aluminum electrode at the surface of the power semiconductor chip by ultrasonic bonding. This is because of providing relatively small damage to the element in the bonding step, and also low cost of both the metalizing step and the wire bonding step, and still more relatively high bonding reliability also.
In a general power semiconductor module having such a wire connecting structure, connecting life-time of an adhered solder layer of a ceramics substrate, and connecting life-time of an aluminum wire determine life-time of a total module. In view of this point, there have been reported that by changing a sealing resin of a power semiconductor, from silicone gel to an epoxy resin, which is a hard resin, stress dispersion and reduction of the adhered solder layer of the ceramics substrate can be attained, and longer-life of the adhered solder layer can be attained (for example, refer to “Selected Failure Mechanisms of Modern Power Modules” by Mauro Ciappa, Microelectronics Reliability 2002, 42: pp. 653-667, or JP-A-2006-179538. Accordingly, at present, a factor determining finally life-time of a power semiconductor module is mainly connecting life-time of an aluminum wire.